Spitzner J R, Chung I K, Gootz T D, McGuirk P R, Muller M T
Ohio State University, Department of Molecular Genetics, Columbus 43210, USA.
Mol Pharmacol. 1995 Aug;48(2):238-49.
The quinolone derivative CP-115,953 [6,8-difluoro-7-(4-hydroxyphenyl)-1-cyclopropyl-4-quinolone-3-carboxylic acid] has been shown to induce eukaryotic topoisomerase II-mediated breaks in DNA, producing cleavage patterns that are distinct from those induced by the anticancer drugs amsacrine, etoposide, and teniposide. High levels of the quinolone have been found to inhibit topoisomerase II activity via an interaction with the enzyme and not by DNA unwinding. Topoisomerase II cleavage sites were analyzed on nine DNA fragments, and 85 quinolone-induced sites were sequenced, as well as 86 amsacrine and 134 teniposide sites. A consensus sequence was derived for the quinolone sites that is different from those reported for other drugs; however, because topoisomerase II cleavage sites are double-stranded but not palindromic, different consensus sequences are not easily compared. For this reason, a new, double-stranded, consensus sequence method, the "unique-base analysis," was developed; this was applied to the quinolone sites as well as six other large sets of topoisomerase II sites determined in the absence or presence of drugs. For each of the seven sets of sites, conserved bases were found in the 16-base region spanning positions -6 to +10, relative to the enzyme cleavage site (DNA breakage between -1 and +1). The conserved bases were virtually identical in the regions flanking the cleavage site for all seven data sets. In contrast, the base preferences identified proximal to the cleavage sites were unique to the drug tested. These observations suggest that the selection of cleavage sites by topoisomerase II involves both enzyme-dependent and drug-dependent recognition elements. The single most preferred base in the quinolone sites was a cytosine at -1; the same preference was found with teniposide, and 60 of the 85 quinolone sites co-localized with teniposide sites.
喹诺酮衍生物CP-115,953 [6,8-二氟-7-(4-羟基苯基)-1-环丙基-4-喹诺酮-3-羧酸] 已被证明可诱导真核拓扑异构酶II介导的DNA断裂，产生与抗癌药物安吖啶、依托泊苷和替尼泊苷诱导的断裂模式不同的切割模式。已发现高浓度的喹诺酮通过与该酶相互作用而非通过解开DNA来抑制拓扑异构酶II的活性。在九个DNA片段上分析了拓扑异构酶II的切割位点，对85个喹诺酮诱导的位点、86个安吖啶位点和134个替尼泊苷位点进行了测序。得出了喹诺酮位点的共有序列，该序列与其他药物报道的序列不同；然而，由于拓扑异构酶II切割位点是双链的但不是回文的，不同的共有序列不容易比较。因此，开发了一种新的双链共有序列方法，即“独特碱基分析”；该方法应用于喹诺酮位点以及在有无药物情况下确定的其他六组大型拓扑异构酶II位点。对于这七组位点中的每一组，在相对于酶切割位点（-1和+1之间的DNA断裂）的-6至+10位置跨度的16个碱基区域中发现了保守碱基。所有七个数据集在切割位点两侧的区域中保守碱基几乎相同。相反，在切割位点近端确定的碱基偏好对于所测试的药物是独特的。这些观察结果表明，拓扑异构酶II对切割位点的选择涉及酶依赖性和药物依赖性识别元件。喹诺酮位点中最优先的单个碱基是-1位的胞嘧啶；替尼泊苷也有相同的偏好，85个喹诺酮位点中有60个与替尼泊苷位点共定位。
